1. Field of the Invention
The present invention relates to an edge detection technique and charged particle radiation equipment. More particularly, the present invention relates to an edge detection technique and charged particle radiation equipment which are capable of stably detecting an edge irrespective of noise, and the like.
2. Background Art
In recent years, the miniaturization of patterns to be inspected has been accelerated according to a tendency to higher integration of semiconductor devices. According to ITRS (International Technology Roadmap for Semiconductors), the physical gate length in an MPU (Microprocessor Unit) is predicted to be 25 nm for 65 nm node, and is predicted to be 18 nm for 45 nm node.
Under the circumstances where the miniaturization is advanced in this way, an actually generated pattern tends to have larger variations in position, width, linearity, and the like, as compared with the design value.
On the other hand, it has become difficult to improve the image quality by the frame addition because of the problem of image quality deterioration due to electrification and contamination of the sample surface, the problem of radiation damage, the demand for throughput improvement, and the like.
Therefore, it is necessary to detect an ultra-fine line and a line having a small luminance change more robustly against noise as compared with before. In patent document 1, there is described a technique for reducing noise by the composite image formation based on the frame addition. Further, in patent document 2, there is also described that smoothing processing is performed to an image in order to reduce noise.
Patent Document 1: JP Patent Publication (Kokai) No. 2007-218711 (corresponding to US2007/0187595)
Patent Document 2: JP Patent Publication (Kokai) No. 2002-328015 (corresponding to U.S. Pat. No. 7,026,615)